Prior to the present invention, polyetherimides were made by effecting reaction between certain aromatic bis(etheranhydride)s and organic diamines as shown by U.S. Pat. No. 3,847,867 (Heath et al.) assigned to the same assignee as the present invention and incorporated herein by reference. Although valuable injection moldable high-performance thermoplastic materials can be made in accordance with the method of Heath et al., new techniques are constantly being developed to further improve the properties of injection-moldable thermoplastics as well as the methods for making such materials.
The present invention is based on the discovery that certain alkylaryl amines having the formula, ##STR1## referred to hereinafter as "DIBDA", where R and R.sup.1 are selected from hydrogen, C.sub.(1-3) alkyl radicals, or a mixture thereof, R.sup.2, R.sup.3 and R.sup.4 are selected from halogen, C.sub.(1-8) alkyl and C.sub.(1-8) alkoxy and mixtures thereof, and a, b and c are whole numbers equal to 0 to 3 inclusive, can be intercondensed with aromatic bis(etheranhydride) having the formula, ##STR2## which preferably includes 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, referred to hereinafter as "BPADA" to produce an injection-moldable high performance polyetherimide having a substantially uniform glass transition temperature, as compared to polyetherimide made in accordance with the teaching of the above-mentioned Heath et al. patent, where R.sup.5 is selected from C.sub.(6-30) divalent aromatic organic radicals. For example, it has been found that the condensation of BPADA with DIBDA, or a mixture of DIBDA with a different organic diamine, such as m-phenylene diamine "MPD", over broad mole percent ranges, results in the production of polyetherimide having substantially the same 217.degree.-220.degree. C. T.sub.g as BPADA-MPD polyetherimide. Advantageously, the mechanical properties of the resulting polyetherimides also have been found to remain relatively constant. In addition, substitution of DIBDA for the more costly MPD has provided significant reductions in the costs for making such polyetherimides.